The status of a poppet valve in regard to:                Its friction behavior in the housing leadthroughs for its adjusting rod(s),        Its pressure and flow forces impinging on the enclosing element or closing elements,        The status of its seat seal(s),        Its drive (integrity of the springs and drive piston, among other things), and        Its other status parametersare reflected in particular in the engagement of the actuation force (action force) of the adjusting rod(s).        
The pressure and flow forces consisting of static pressure (overpressure, underpressure) and/or dynamic pressure (inflow) comprise the planned forces that result during the regular operation of a processing system in which the poppet valve is arranged; however, they also comprise unplanned forces such as pressure surges or shocks in the valve housing supplied with the respective fluid. These unplanned forces can exceed the planned ones many times over, they affect the relevant closing element and hence the adjusting rod that is fixedly connected thereto, and they also influence the interaction between and equilibrium of forces in the drive unless they are largely compensated by so-called pressure balanced pistons, or experience corresponding opposing forces from the seat surface of the closing element.
A measuring system is described in DE 298 11 115 U1 for measuring the spindle force in fittings in which, among other things,                a force sensor is arranged in a frictional connection at a position in the direction of force of the acting spindle force,        The force sensor can be a strain gauge,        The force sensor is, for example, mounted on the spindle or on a connecting screw in the flange between the fitting and drive.        
In addition to the strain gauge functioning as the force sensor, the known measuring system has a calibration measuring device with which the force sensor is calibrated. The calibration measuring device is removed while the system is operating. The object of the described measuring system is to provide a measuring system that is optimally suitable for the measuring procedure in WO 96/30684 A1 in which the spindle force is measured in situ and evaluated using procedures for analyzing the time signal, and furthermore enables the spindle force to be continually measured.
A specific solution of how to measure the spindle force of a valve driven by a spindle/nut system is only disclosed in conjunction with a calibration measuring device. Beyond that, only a force sensor is described that can be mounted to a connecting screw on a flange between the fitting and drive. Whether such an arrangement is suitable to, for example, reliably detect a defect in the seat seal, a worn or corroding rod leadthrough, an incomplete closing, opening or partially open position (seat cleaning), or a pressure surge is not disclosed, discussed or suggested.
A diagnostic method is known from U.S. Pat. No. 4,882,937 A which is based on a force-movement curve. The movement of the valve rod in a sensor which basically consists of a coil with a plurality windings, induces stress which is proportional to the speed of the axial movement of the valve piston. A speed-time curve is accordingly determined that is combined with the speed-time curve which is also measured. The actuating force of the valve rod is not directly measured; instead, a suitable sensor measures its reaction force which arises in a connecting housing between a valve housing and a drive which causes the actuating movement of the valve piston.
Specific solutions for achieving a practical diagnostic method for poppet valves having a spring piston drive supplied with pressurizing medium and a measuring device for performing it are consequently not disclosed in the aforementioned prior art. The aforementioned prior art also does not disclose any indications and suggestions of how to glean such information from the obtained measuring signals.
Based on the state-of-the-art, the object of the present invention is to provide a diagnostic method for poppet valves of the generic type with which the status of a poppet valve e.g. regarding                its friction behavior in the leadthroughs for its adjusting rod(s),        the status of its seat seal(s),        mechanical damage to its interacting components (such as springs in the drive; spring failure)        the displacement position of its closing element/closing elements during its switching cycles and/or        events such as the occurrence of pressure surges or shocks in ongoing operation,are continously monitored, the measuring signals are saved and the saved measuring signals are usefully interpreted, and early notification of damage is provided. It is furthermore the object of the invention to present a measuring device to perform the diagnostic procedure with which the aforementioned states and events can be reliably and reproducibly detected.        